Kaluza-Klein graviton phenomenology for warped compactifications, and the 750 GeV diphoton excess

TL;DR

This paper investigates whether the 750 GeV diphoton excess observed at the LHC could be explained by a warped Kaluza-Klein graviton, analyzing its phenomenology and compatibility with existing data.

Contribution

It explores the potential of warped extra-dimensional models to account for the 750 GeV excess, providing a simplified model with parameter estimates and confronting it with experimental results.

Findings

Best-fit coupling scale $\\Lambda \approx 60$ TeV.

Some tension with 8 TeV and dilepton data, but not excluded.

Predicted signals should appear in diphoton and dilepton channels soon.

Abstract

A generic prediction of scenarios with extra dimensions accessible in TeV-scale collisions is the existence of Kaluza-Klein excitations of the graviton. For a broad class of strongly-warped scenarios one expects to initially find an isolated resonance, whose phenomenology in the simplest cases is described by a simplified model with two parameters, its mass, and a constant $\Lambda$ with units of mass parameterizing its coupling to the Standard Model stress tensor. These parameters are in turn determined by the geometrical configuration of the warped compactification. We explore the possibility that the 750 GeV excess recently seen in 13 TeV data at ATLAS and CMS could be such a warped Kaluza-Klein graviton, and find a best-fit value $\Lambda\approx 60$ TeV. We find that while there is some tension between this interpretation and data from 8 TeV and from the dilepton channel at 13 TeV, it is not strongly excluded. However, in the simplest scenarios of this kind, such a signal should soon become apparent in both diphoton and dilepton channels.